This invention relates to Network Synchronization Control Systems for communicating between computer networks, and more particularly to a Network Synchronization Control System for communicating between Local Area Networks (LAN), and between LAN and Wide Area Networks (WAN).
LANs are centralized networks comprised of a communication or transmission line which is shared by a number of nodes, including by way of example work stations, peripherals and file servers. Each node in the network has a unique address, and its reception circuitry constantly monitors the transmission line to determine whether a message is being sent to the node.
A Wide Area Network (WAN) is a computer network that uses high-speed, long-distance communication networks such as those of communication satellites or microwave channels to interconnect nodes including LANS over distances greater than those traversed by LANs alone.
In communicating between LANs, or between a LAN and a WAN, the different clock times of the respective networks must be reconciled before information including voice or image data may be transferred without loss of integrity.
In prior systems, clock signals from an External Network are fed to a control node or sub-control node of a Local Network. Normally, the Control Node supplies the clock signals to all nodes in the Local Network, and the sub-control node supplies the clock signals when the Control Node is inoperative. Such a system is disclosed in Japanese Patent Application No. 21538971987.
In the above prior art, as only two nodes (the control node and the sub-control node) may receive clock signals from the External Network, the ability to design a network system is severely confined. Further, upon both the Control Node and the sub-control node becoming inoperable, meaningful communication with the External Network ceases.